Solved: Internet: pages slow/failing to load, videos not playing

Tech Support Guy System Info Utility version 1.0.0.1 OS Version: Microsoft Windows 7 Home Premium , Service Pack 1, 64 bit Processor: Intel(R) Core(TM) i3 CPU M 330 @ 2.13GHz, Intel64 Family 6 Model 37 Stepping 2 Processor Count: 4 RAM: 2806 Mb Graphics Card: Intel(R) Graphics Media Accelerator HD, 1275 Mb Hard Drives: C: Total - 146426 MB, Free - 117863 MB; D: Total - 146427 MB, Free - 146333 MB; Motherboard: Acer Aspire 5741 V1.02, Base Board Serial Number Antivirus: AntiVir Desktop, Updated and Enabled Hi, I've recently got both broadband and my new laptop up and running. After a few days of everything working fine, it's gone to pot. Pages are randomly loading very, very slowly or not at all, though sometimes loading fine if I hit refresh. Further, any video will buffer fine, play for 30 - 120 seconds then stop, say it is buffering and refuse to play. Downloads will randomly be ok or extremely slow. I spent 4 days on the phone to the tech support for my broadband company. We've established that there is nothing wrong with my internet connection or wireless (we even tried going through all the channels) and speed tests are showing real download/speeds of around 8Mbps. My flatmate's internet is working no problem. I thought it could be a problem with firefox and the add-ins I have (NoScript, Cookie Monster, Unplug, McAfee Site Advisor), although everything is up to date and I had consistently cleared the cache. So I downloaded IE and used it 'clean': same result. Avira and Malwarebytes scans are showing nothing. Windows and PC Tools firewall are fully updated and hard drive is defragged. What's going on? Please help!

Thank you so much! The PC Tools firewall seems to have been causing it. I've uninstalled it (just through Control Panel>Progs and Features>Uninstall) and switched Windows Firewall back on. Do I need to do anything else? Should I just keep using Windows Firewall (and should I also switch on Windows Defender)?